The elongation phase of transcription by RNA polymerase II (Pol II) is highly regulated and intricately integrated into mRNA biosynthesis. In an effort to understand the factors involved and their mechanisms of action, studies are proposed that will help understand the role of P-TEFb and TTF2 in controlling transcription elongation and to what extent RNA processing is functionally coupled to transcription. I. P-TEFb plays a key role in regulating the critical checkpoint to productive elongation that occurs shortly after initiation. The kinase activity of P-TEFb is in turn uniquely regulated by reversible association with an RNP which contains 7SK RNA and HEXIM1 or HEXIM2. Parameters affecting the formation and dissociation of the P-TEFb/7SK/HEXIM complex will be examined using methods in vitro and in vivo. Details of the function of P-TEFb on specific genes and globally over all genes will be gathered using nuclear run-on reactions coupled to array methods. II. Transcription is shut off during mitosis and the RNA Pol I and Pol II termination activity of TTF2 is required for mitotic repression of transcription elongation. The role of TTF2 in mitotic transcription repression will be further studied and potential roles in transcription coupled repair, and interphase transcription will be examined. Also the potential role of TFIIF and other elongation factors in controlling TTF2 activity during transcription will be investigated. III. The processing reactions needed to generate functional mRNAs occur in part during elongation and are influenced by the transcription process. Newly developed assays will be used to elucidate the details of the function of the human capping enzyme and the cap methyl transferase in the context of transcription. Finally, using a newly developed in vitro system we will determine the extent to which polyadenylation is functionally coupled to transcription elongation and termination. Most of the studies described are aimed at understanding basic processes controlling gene expression, but P-TEFb plays a major role in HIV gene expression and may be a target for AIDS therapy. Also because a drug in clinical trials for cancer therapy, flavopiridol, targets P-TEFb, the proposed studies are important. [unreadable] [unreadable]